Yes agree with the other girls. If its money that wasn't paid in the past it turns into debt he will have to pay now so it means although he is still supporting other children (younger) then any outstanding money is added to start paying of the debt from the past. It use to be 18% of the wage I think years ago (and a little bit more per child) so it depends on his income as to how much he pays and of course any outstanding money that hasn't been paid in the past and I guess if you times it by 6children then it would be a very large portion of his income that would be paid out in child support. If the money hasn't been paid at some stage it does accumulate quickly especially if there was several years of not paying in the past.

I am going through a similar thing at the moment but am on the other end (the parent that has not received the support) from my ex it now has turned into a very large sum of money (from 8yrs of not paying) there are ways to reduce what he owes from now on (although not from what is owed in the past) examples include having the children for X amount of days a month, private agreement with the other parent etc. Perhaps encourage him to call CS and see ways in which he can reduce his payments.